Lug Nut Torque

Had a tire worked on less than two months ago and went to rotate them myself only to find that one of the lug nuts was on too tight to be removed by hand. I use a cross-bar lug wrench and I'm not a weakling.

I took it back to the tire dealer and complained loudly about their poor work. They are of course ducking responsibility and claiming that the "torque sticks" they use on the impact wrench correctly torque the lug nuts. They showed me a nice color-coded chart that lists the automobile make and model, the colored socket to use and the amount of torque that should be applied.

I looked over the extension they were using and concluded that it was only a solid piece of metal with no special torque properties -- no ratchets or anything. They insist that the extension has some property that prevents excessive torque. I should have looked more closely at their nice color-coded chart. I'd be willing to bet that they same extension is specified for use on different cars with different torque ratings. I wish I'd thought of that when I was debating it with them.

So, am I right? The nice kit full of color-coded extensions is for different sizes of lug nuts, right? The dealer makes a big deal about how they are doing it right and nobody else in town is. Their guys don't tighten lug nuts evenly using a star pattern either (which is also on the nice color-coded chart). They're either ignorant or deliberately misleading people. I'd like to get in touch with the vendor(s) of these wrench extensions and have them get in touch with this tire dealer to straigten them out. Anybody know who the manufacturer(s) or vendor(s) are?